Effect of long-term amiodarone therapy on thyroid hormone levels and thyroid function.

Area of Science:

• Cardiology
• Endocrinology
• Pharmacology

Background:

• Amiodarone is a widely used antiarrhythmic medication.
• Thyroid dysfunction, including hyperthyroidism and hypothyroidism, has been reported in patients treated with amiodarone.

Purpose of the Study:

• To prospectively evaluate the frequency of thyroid abnormalities in euthyroid patients receiving amiodarone.
• To assess the impact of amiodarone on thyroid hormone levels and actual thyroid function.

Main Methods:

• 45 euthyroid patients were monitored for 12-27 months during amiodarone therapy.
• Serum samples were analyzed for thyroxine, thyrotropin, triiodothyronine, and triiodothyronine resin uptake.
• Patients were categorized into groups based on thyroid hormone levels.

Main Results:

• Virtually all patients exhibited changes in thyroid hormone levels.
• Chemical hyperthyroidism occurred in 4% of patients; clinical hyperthyroidism was not observed.
• 9% of patients developed both biochemical and clinical hypothyroidism.
• Older age was associated with elevated thyroxine and thyrotropin levels.

Conclusions:

• Amiodarone significantly influences thyroid hormone parameters but less frequently alters actual thyroid function.
• While overt hyperthyroidism is rare, amiodarone-induced hypothyroidism occurs in a significant minority of patients.
• Monitoring thyroid function is crucial for patients on amiodarone therapy.